1. Field of the Invention
The present invention relates to manufacturing of a semiconductor device, and particularly, relates to a metal polishing liquid and a method for chemical mechanical polishing of metal in the wiring process of a semiconductor device.
2. Description of the Related Art
In the development of a semiconductor device represented by the semiconductor integrated circuit (hereinafter the term LSI is used), a higher density and a greater integration by making the wiring finer and stacking wiring have been demanded for more compact size and increased speed. In recent years, an LSI using copper, which has a low wiring resistance, as a metal for wiring has been developed. As the art for this, various techniques, such as the chemical mechanical polishing (hereinafter to be abbreviated to the CMP), and the like, have been adopted.
The CMP is an art for flattening the irregularities of the wafer surface that have been produced by stacking. The general method attaches a polishing pad to a circular polishing platen, wets the surface of the polishing pad with a polishing liquid, and presses the surface of the substrate (wafer) against the pad. Thereafter, from the rear face thereof, a prescribed pressure (polishing pressure) is applied, and both the polishing platen and the substrate are rotated for generating a mechanical friction by which the surface of the substrate is flattened.
The metal polishing liquid for use in CMP generally includes abrasive grains (made of, for example, alumina or silica), and an oxidizing agent (for example, hydrogen peroxide). Such a metal polishing liquid is considered to serve for polishing by oxidizing the metal surface with the oxidizing agent, and removing the resulting oxide film with the abrasive grains.
However, the use of such a metal polishing liquid for performing the CMP causes the insulating material between metal wirings to be polished more than required, producing polishing scratches, a phenomenon in which the entire polishing surface is polished more than required (thinning), or a phenomenon in which the entire polishing metal surface is not flattened, and only the central portion of the polishing metal surface is polished more deeply, resulting in a dish-like recess being produced (dishing). Further, a phenomenon, such as that in which a plurality of wiring metal surfaces form a dish-like recess (erosion), or the like, may be caused. Especially in recent years, because a still higher density and a still greater integration have been schemed, the request for reduction in dishing amount is becoming more and more strong. In addition, recently, for enhancing the productivity, the wafer diameter at the time of LSI manufacturing has been increased. Therefore, at present, a diameter of 200 mm or more is generally used, and manufacturing with a diameter as large as 300 mm or more has been commenced. With such an increase in size, the difference in polishing speed between the wafer central portion and the peripheral portion has been increased, and thus the demand for improvement in uniformity throughout the surface has become stringent. Further, recently, there has arisen a demand for a method which assures a sufficient polishing speed even when the polishing is performed with the pressure being lowered in order to prevent film peeling from being caused, even for an insulating material having a low mechanical strength.
To solve such problems, a metal polishing liquid which includes no abrasive grains, and is made up of hydrogen peroxide, malic acid, benzotriazole, ammonium polyacrylate, and water is disclosed in Japanese Patent Laid-Open Publication 2001-127019. According to this method, a conductor pattern with which a metallic film remains in the recess can be obtained. However, a problem that it is difficult to obtain a sufficient polishing speed has been left unsolved. In Japanese Patent Laid-Open Publication No. 2001-279231, a water-based dispersion for chemical mechanical polishing that contains an organic compound which suppresses the degradation of the polishing pad is disclosed. However, there remains a possibility of occurrence of the dishing phenomenon. As the dishing suppression method, a method which first performs the first-stage polishing at room temperature, and then lowers the system temperature to perform the second-stage polishing, thereby suppressing the dishing is disclosed in Japanese Patent Laid-Open Publication No. 8-83780/1996. However, an expensive process cost is involved, and no versatility is provided.